DE736380C - Fuel injection pump - Google Patents

Description

The invention relates to a fuel injection pump with two hydraulically coupled Pistons, one of which (drive piston) is driven directly by the internal combustion engine to which the pump belongs and in turn the second (injection piston) at least in the first part of the Working stroke, drives via a fluid cushion that binds the hydraulic clutch represents the two pistons. The second piston is the piston that delivers the fuel worried into the injection line.

Such fuel pumps are inherent

known. It is also with these pumps

x5 also known as the fluid content of the between the two hydraulically coupled pump pistons located liquid cushion to change in this way constant stroke of the drive piston the amount of the pumped To change fuel. For the purpose of changing the liquid content of the liquid cushion becomes the relative position of the inlet opening opening into the space of this liquid cushion to that controlling it Front edge of the drive piston adjusted in such a way that the inlet opening of which in turn from the internal combustion engine speed-dependent driven drive piston is completed sooner or later.

With this known scheme of the λ'οη The amount of fuel delivered by the pump is inevitably also a change in the beginning connected to the injection. It therefore exists in these known regulating devices a certain relationship between the amount of fuel injected and the start of fuel injection, but there is no specific relationship between the start the fuel injection and the speed of the fuel pump driving Internal combustion engine.

The purpose of the present invention is in internal combustion pumps with two hydraulically coupled piston automatically depending on the speed of the Internal combustion engine, to which the fuel pump belongs, the start of fuel injection to regulate in such a way that this beginning is earlier, the greater the engine speed is without

in advance of this postponement of the start of fuel injection, inevitably the amount of fuel injected Fuel is changed.

According to the invention this is achieved in that for the automatic control of the Injection time to the space containing the liquid cushion except for the refill opening a throttled outlet opening is connected in such a position that it depends on the speed of the internal combustion engine connected drive piston only after completion of the refill opening and after the drive piston has already been a part of its inward stroke back-'5 is completed and for regulation the injection quantity in a known manner, the promotion by opening a Return flow opening is interrupted sooner or later. This throttled outlet opening allows a greater amount of liquid to escape through the drive piston before it is completed, the smaller the amount Speed of said piston, i.e. the lower the speed of the internal combustion engine is, so that accordingly the liquid content remaining in the liquid cushion is also the smaller and The lower the piston speed, the later the start of injection. the Throttling of said outlet opening has the effect that the differences in the amounts of liquid pushed out through this opening in the usual speed range an internal combustion engine are large enough to accommodate one for practical needs bring about sufficient variability in the start of injection.

It is already known for fuel injection pumps that have only one piston work to arrange a slot in the piston through which, depending on the speed of the pump piston a more or less large amount of fuel flows out of the pump cylinder, in fact all the same more, the lower the piston speed is. This will change the beginning the injection achieved, but this is a function of the piston speed and the Represents amount of fuel. This means that it is not possible, regardless of the amount of fuel to achieve control of the start of injection solely through the piston speed for any loads.

The invention is illustrated in the drawing, for example, and that serves

FIG. 1 only to explain the invention underlying thought while the

Fig. 2 to 6 illustrate various pumps designed according to the invention in section.

In Fig. Ι a pump is shown purely schematic, in which in a cylinder 1 two pistons 2i _e and 21 _{6 are} displaceable. Of these two pistons, the piston 21 is driven, for example by a cam 2 of the internal combustion engine to which the pump belongs. The cam 2 has an unchangeable position with respect to the crankshaft of the internal combustion engine, so that the various positions of the piston zi _a always have a certain relationship to the position of the pistons in the internal combustion engine cylinders.

The piston 2i _ß drives the piston 2i _Ä via a liquid cushion F, which piston in the pump according to FIG. 1 is the piston which conveys the fuel. The piston 2Ij is provided in a known manner with inclined control surfaces 23 and 24 which cooperate with a fuel inlet line 25 which opens into the actual pump chamber of the fuel pump.

The fuel injection begins at the moment in which the upper control _{edge 23 of the piston 21 6} covers the mouth of the line 25, and stops when the lower control edge 24 uncovered the mouth of the line 25 again. The length of the fuel conveyed depends on the distance between the control edges 23 and 24 along those generators that cooperate with the mouth of the line 25.

The beginning of the fuel injection with respect to the position of the drive cam 2 and the associated position of the piston in the internal combustion engine cylinder fed by the fuel pump depends on the distance of the edge 23 of the piston 2I ₆ from the opening 25. This distance in turn depends on the height d of the liquid cushion F under otherwise identical conditions. The greater this height * /, the smaller the distance between the piston edge 23 and the opening 25 and the sooner the fuel injection begins, while the fuel injection takes place later, the smaller the height d mentioned . The start of the fuel injection can thus be shifted by changing the liquid content of the liquid cushion F and thus by changing the height d of this liquid cushion. This postponement of the start of the fuel injection has no influence on the amount of fuel delivered, since in the case of the pump described this depends only on the axial distance between the parts of the control edges 23 and 24 that are currently active.

Proceeding from the conditions explained above, the present invention is now carried out

proposed to make the content of the liquid cushion F variable as a function of the engine speed in order to regulate the start of the fuel injection as a function of the engine speed, while the injection quantity is regulated in a manner known per se by opening a return flow opening earlier or later,

ίο which ends the effective pump stroke will.

Exemplary embodiments of the invention are shown in FIGS.

In the exemplary embodiment according to FIG. 2, the space containing the liquid cushion between the pistons 2i _ß and 2i ₆ is denoted by 22. In the wall of the cylinder 1, two lines 26 and 33 are connected at the point at which the intermediate space 22 is located at the beginning of the working stroke of the pistons 2i _ß and 2i _&. The line 26 is in the low position of the piston 2i _ß (see the position shown in Fig. 2) immediately above the face of said piston and serves to fill the liquid content of the chamber 22 at the beginning of each working stroke to a certain initial value. For this purpose, the line 26 opens into the fuel feed

3c chamber 27, in which also the fuel supply line 25 opens.

The second line 33, which opens into the space 22 in the lower position of the pistons 2i _a and 2I _6, is slightly higher than the line 26 and represents a throttle line that opens into a space 32, the outlet of which is closed by a valve 34 which is through a spring 35 is pressed onto its seat. The force of the spring 35 can be regulated by a screw 36.

The pump of FIG. 2 also includes a spring 29, which strives _{to keep the piston 21 &} in its low position. Furthermore, a rack 28, which is _{in engagement with teeth 30 of the piston 2i s} , is used in a known manner to rotate the piston about its axis in order in this way to determine the effective distance between the control edges 23 and 24 and thus the injected To be able to change the amount of fuel. Finally, the pressure line 9 leading to the injection nozzle is connected to the actual pump chamber of the pump via a check valve.

The operation of the device according to FIG. 2 is as follows. When the piston 2i _ß has left the low position shown in FIG. 2 at the beginning of its upward movement, it first closes the refill opening 26 . With the further upward movement of the piston 2i _a becomes a. Part of the liquid enclosed in the space 22 is expelled through the throttle opening 33. With a constant cross section of the throttle opening 33 and with a constant pressure of the spring 35, the amount of liquid expelled from the space 22 _{depends on the speed of the piston 2 i ß} . If the speed of the piston 2i _{a is} very low, all of the _{fluid displaced by the piston 2i ß} after the line 26 has been closed is driven out through the throttle line 33 and the valve 34, which is open against the pressure of the spring 35. The piston 2I ₆ thus remains in the lower position shown in FIG. 2 until the piston 2i _e has also covered the line 33. Only then is the movement of the piston 2i _a transmitted to the piston 2i ₆ , and the latter moves upwards together with the former. The fuel delivery begins at the moment at which the control edge 23 covers the line 25. However, if the speed of the piston 2i _{a is} greater, then, always provided that the cross section of the throttle line 33 and the pressure of the spring 35 remain constant, not all of the _{fluid displaced by the piston 2i a} through the line 33 and the valve 34 exit, but the movement of the piston 2I ₆ begins before the end of the line 33 through the piston 2i _fl . Remaining in the fluid cushion 22 Flüs'sigkeitsmenge and thus the pressure maintained by the fluid cushion gap between the piston 21 ₀ and 2i, j are all the greater, the greater the speed of the piston 2 i _a, so that the cover of the conduit 25 through the control edge 23 occurs all the sooner, the greater the speed of the piston 2i _a . Is thus obtained without any influence from the outside, by only inside the pump existing means, a control of the injection timing in response to the "speed of the pump piston 21 ₀ and in turn driving in dependence on the speed of the-called _ th pump piston internal combustion engine.

The screw 36 is used, either as expressly stated merely for adjusting the tension of the spring 35 so that the law which determines the dependence between the Brennkraftmaschinengeschwindig ¹ -keit and the date of start of injection can be changed with their help. But once this law is determined by a certain tension of the spring 35, the regulation according to this law takes place completely automatically without any influence on the spring tension. To regulate the above-mentioned law of dependency, one could also use the width of the spring 35 instead of the tension

Throttle opening 33 or act on the tension of spring 29

The pump of FIG. 3 differs from that of FIG. 2 mainly in that According to FIG. 3, the line 26 simultaneously takes over the function of the line 33, too for which purpose the line 26 in the embodiment of FIG. 3 is arranged higher is than in the embodiment according to FIG. 2.

In addition, the outer mouth of the line 26 is under a function of the Internal combustion engine speed variable pressure. For this purpose, the fuel feed chamber 27 is in a liquid circuit switched on, that of a not shown in the drawing · and proportional the engine speed driven pump is maintained. The supply line of the circulating combustion

sso substance liquid into the chamber 27 takes place through the line 41 and the discharge of the fuel liquid takes place through the line 44. The direction of the liquid cycle is indicated by the arrows drawn.

Furthermore, in the chamber 27 is in the direction of the liquid circuit behind the mouth the line 26 is provided with a throttle point which is formed by a channel 42 and an adjusting screw 43. In that one Part of the chamber 27, which is located in front of the aforementioned throttle point, thus occurs the higher the pressure, the greater the speed of the internal combustion engine.

This pressure acts exactly in the same sense as the speed of the piston 2i _a , that is, the greater the pressure at the outer end of the line 26, the lower the amount of liquid that emerges from the cushion 22 into the chamber 2 ^ if the piston 2i _a makes its upward movement. The result is the same as in the subject of FIG. 2, ie the liquid cushion 22 and thus the distance between the pistons 2 1 and 2 ₆ are greater the greater the engine speed, so that the fuel injection begins the sooner the greater the engine speed.

The adjustment of the size of the throttle opening in the line 42 by adjusting the Regulating screw 43 has the same effect as that in the embodiment of FIG Adjustment of the tension of the spring 35 in the embodiment of FIG. H. by this setting becomes "the law which determines the dependence between the beginning of the Fuel injection and engine speed controls, modified.

The embodiment according to FIG. 3 also has the effect that the upper speed limit of the internal combustion engine is automatically set in it. If the speed of the internal combustion engine has become so rapid that the pressure in the chamber 27 of the spring 29 is in equilibrium, it can _{no longer push the piston 2I 6 down} into its lower position after the end of the work, so that no fuel is drawn into the Pump chamber of the pump takes place more, and the fuel delivery is thus interrupted.

In the embodiment of Fig. 4, the piston 2i _a carrying instead of the piston 2i _6, the fuel quantity controlling control edges 21 and 24. The piston 2i ₆ has to delay in this case mainly the task of the beginning of the injection, even if it has already been set in motion _{by the piston 2i ß} via the hydraulic cushion 22. For this purpose, the piston 2i _{6 is provided} with a part 52 which completely closes off the cylinder 1 and which only allows the liquid displaced by the piston 2i _{a to} enter the space above it when its part 52 has released grooves 53. The maximum delay in fuel injection is given by the distance between the stops 51, on which the piston 2I ₆ rests in its rest position, and the lower edge of the grooves 53.

Open into the buffer chamber 22 as well as two lines in the embodiment of FIG · 2 at different heights covered _ß in the embodiment of Fig. 4 26 and 33, one of which is the lower the replenishing line and at the beginning of the working stroke of the piston 2i while the upper one represents the throttle line, which has the same function as in the cases discussed above.

The mode of operation of the object of FIG. 4 is as follows: When the internal combustion engine is very slow, all the fluid displaced from the piston 2i _a after the end of the ^IO 5 line 26 is driven out of the cushion 22 through the throttle line 33, so that the piston 2i ₆ remains on its seat 51 until the upper edge 23 of the piston 2i _ß the line 33 has completed. From this moment on, the piston 2ij is _{hydraulically coupled to the piston 2i ß} , but fuel can only be delivered after the lower edge of the part 52 of the piston 21 _{6 has released} the lower edge of the lines 53. This is because 21 ₆ of the same in the \ Orangegangenen return stroke of the piston above a void is created that is exactly equal to the stroke volume, which makes the piston _2i in the described first 'part of its upward movement. However, if the speed

speed of the piston ζτ _{α is} greater than the minimum speed _{under consideration, the piston 2I 6} begins its upward movement against the action of the spring 29 before the throttle line 33 is covered by the piston 2I ₀ , the earlier the greater the speed of the piston 2i _a . As a result, in the case of the subject of FIG. 4 as well, the start of the injection occurs all the sooner, the greater the speed of the piston 2i _a . In all cases, the injection stops at the moment in which the lower control edge 24 releases the line 26.-

In the subject of FIG. 5, apart from an automatic control of the start of injection also ensured that the engine does not exceed a certain maximum speed.

In the embodiment according to FIG. 5, the pistons 2i _a and 2I _{6 are shown} in a position in which they have already covered a certain part of their upward movement. In addition, the distance d between the two pistons has the value that of the greatest permissible engine speed is equivalent to.

_{In the subject of FIG. 5,} too, two lines 26 and 33 are provided _{which open into the liquid cushion between the pistons 2i a} and 2i 6 in the lower position of the latter. The function of these lines is the same as that of the lines identified in the same way the objects of FIGS. 2 and 4.

The essential feature of the device according to FIG. 5 is that a line 65 is connected to the pump chamber 66, which in turn opens into the part of the inner wall of the cylinder 1 in which the upper part of the piston 2i _a moves. The upper part of the piston 2i _a is provided with a constriction and an inclined control edge 64 and is rotatable about its axis in the usual way. When the piston 2 i _{a is in} the position shown in FIG. 5, the edge 64 covers the mouth of the channel 65 at all speeds at which the height of the liquid cushion is less than the height shown in FIG Control edge 23 of piston 2i ₆ covers line 25. Up to -. The speed d of the shown in Figure 5 height corresponds to the liquid cushion, so the control of the start of injection is done in exactly the same way as for example in Figure 2. However, if the distance between the two pistons 2i _a and 2I. ₆ 5 exceeds the value d shown in FIG. 5, which corresponds to a further increase in the engine speed, after the line 25 has been covered by the control edge 23 of the piston 2I _6, the lower opening of the line 65 is still open, so that some of the conveyed Fuel liquid can escape through the line 65 and thus the engine speed is prevented from exceeding the limit value established _{by the setting of the piston 2i a.} This limit value of the permissible internal combustion engine speed can be changed by rotating the piston 2i _{a about its axis.}

The embodiment of FIG. 6 differs from the embodiments of FIG Figures treated above in that the promotion of the amount of fuel in the The subject of Figure 6 occurs in two sections. The first section only says promoted a relatively small constant amount of liquid, the start of injection is variable as a function of the speed of the internal combustion engine, during the time of the main injection taking place in the second section the speed of the internal combustion engine is not influenced.

In the embodiment according to FIG. 6, the piston 2i _{6 has} a disk-shaped part that fills the interior of the cylinder 1. Furthermore, the piston 2 i _{a is provided} with a control edge 71, which determines the end of the main injection period in cooperation with the channel 65. When the pistons are in the low position, the lines 26 and 33 open into the space containing the liquid cushion.

The operation of the device according to FIG. 6 is as follows.

During the upward movement of the piston 2i _ß the piston 2I ₆ after the opening 26 is closed by the liquid cushion between 100. See the two pistons _{sooner or later, depending on the speed of the piston 2i a} , as shown in detail with reference to the above described figures has been set forth. At the moment when the disc-shaped lower part of the piston 21 ₆ loops over the line 25, a brief first injection takes place, namely the amount of fuel injected in this first period corresponds to the height of the disc-shaped part of the piston 21 ₆ . As soon as the underside of the piston 21 ₆ lies above the line 25, the further movement of the piston 21 ₆ ceases, as the liquid still contained in the space between the _{piston 2i a} and 2i ₆ when the piston 2i _{( (} is expelled through the opening 25. When the piston 2i _{ß has} finally risen so far that its top lies against the underside of the piston 21 ₆ , the main injection period begins, which ends therewith

that the control edge 71 releases the lower mouth of the line 65.

It thus follows that in all of the embodiments described above Invention a depending on the internal combustion engine speed, automatic control of the start of fuel injection is achieved without this nor are any special regulators necessary, rather the automatic one Regulation exclusively with the help of the organs of the fuel pump itself.

The embodiments according to the invention which work with a throttle line 33 also have the advantage that they also have an automatic adjustment of the Time of fuel injection results in the heat condition of the engine. Ever Namely, the warmer the fuel, the lower its viscosity and the greater is the amount of fuel escaping through line 33. The consequence of this is that the Advancing the fuel injection with increasing speed with a warmer one Machine is smaller than with a colder machine · This automatically adjusts to the in Dependence on the state of heat. of the engine variable ignition delay in the combustion chamber Taken into account. Finally, it should be emphasized again that in the foregoing only exemplary embodiments of the invention are described, to which this' is not limited.

Claims (5)

. Patent claims: i. Fuel injection pump with two pistons, one of which is driven by the internal combustion engine to which the pump belongs, depending on the speed, while the second, which delivers at least the first part of the fuel injected in each injection period, at least at the beginning of its stroke of the. first piston is driven via a liquid cushion, the space of which is provided with at least one refill opening, characterized in that a throttled outlet opening (33) also opens into the space occupied by the liquid cushion (22), which is arranged in such a way that it is only after Completion of the refill opening (26) is closed by the piston (2i _e ) driven as a function of the speed of the internal combustion engine after the last-mentioned piston has covered part of its inward stroke. 2. Pump according to claim i, characterized in that the additional outlet '33) ⁷ - ^{u leads to} a chamber (32) with a valve-controlled outlet opening, the tension of the spring holding the valve (34) in its closed position 35) adjustable is (Fig. 2). 3. Pump according to claim 1, characterized in that the _{pump chamber located above the intermediate piston (2I 6} ) is connected by a channel (65) to an opening which can be closed by a control surface (64) of the driving piston (2i "), while the intermediate piston controls a fuel inlet and outlet opening (25) leading to the same pump chamber (Fig. 5'j. 4. Pump according to claim 1 with separate pre- _{injection and main injection, characterized in that the intermediate piston (2I 6} ) has a disk-shaped part, the height of which corresponds to the amount of fuel to be injected during the pre-injection and which loops over a fuel inlet opening (25) in the first part of its inward movement , the fuel quantity to be injected during the pre-injection is conveyed during the grinding of the inlet opening, and that the intermediate piston (2ΐ _Λ ) continues after the opening (25) has been reopened and the liquid cushion is pushed through this opening directly by the driven piston (2i ″) is driven. 5. Pump according to claim 1, characterized in that the outlet opening of the Liquid cushion (22), which is only completed after the immediately Connected to the internal combustion engine "pump piston (2i") part of its inward Directed stroke has traveled, for the purpose of throttling it is connected to a chamber (27 ') in which a there is a fluid pressure dependent on the internal combustion engine speed (Fig. 3). 6 · Pump according to claim 5, characterized in that the chamber (27) in a flow of liquid is switched on, which is passed through one of the internal combustion engine driven pump is kept in circulation, and that in the liquid flow behind the point at which the outlet line opens, an expediently controllable throttle point (42, 43) is switched on (Fig. 3). 1 sheet of drawings